1. The Field of the Invention
The present invention relates to a communications system including a plurality of telecommunications networks. The networks provide subscriber terminals with publicly-known telephone numbers. Each network allows selected subscriber terminals registered therewith to be associated together in a group (for example a private dialing plan or virtual private network (VPN)). This may enable those subscriber terminals to address communications to one another using a respective code allocated to each of the selected subscriber terminals. For example, this can be a short dialing code or a code corresponding to an extension number also used for making internal telephone calls on a fixed telephone network.
2. The Background of the Invention
It is known for a mobile telecommunications network to provide selected (A subscribers (for example, those belonging to a particular organization or company) with a private dialing plan or VPN. The subscribers within the VPN can address communications to one another using a code which is different to the publicly-known telephone number allocated to each of the subscriber terminals. The code will typically be a short dialing code (for example, a four-digit code corresponding to the extension number of the user of the subscriber terminal in the fixed internal communications network of the organization). Further, or alternatively, subscriber terminals within the VPN may be provided with special services not available outside the VPN and may be charged by the mobile telecommunications network on a different basis from subscribers which are not in the VPN.
Whilst such arrangements are convenient, such systems only allow subscribers of the network hosting the VPN to access the VPN (that is, to be able to address calls to other subscriber terminals using the codes).